High molecular weight salivary mucins (MG1s) are multimeric glycoconjugates secreted by specialized acinar cells in submandibular, sublingual and minor salivary glands. In the oral cavity, mucins protect oral surfaces against desiccation, form a selectively permeable diffusion barrier between underlying surfaces and the external environment, lubricate hard and soft tissues to minimize mechanical injury, facilitate speech and swallowing, and provide a physical barrier to protect against colonization of potentially harmful microbes and viruses. Mucins have been difficult to isolate and characterize because of their large size, polymeric state and high oligosaccharide content. No information is available on the structural organization or primary structure of high molecular weight salivary mucins although there is mounting evidence that unmistakably points to existence of distinct mucins in human submandibular and sublingual glands. Recently, the Principal Investigator has isolated and sequenced clones encoding portions of a high molecular weight mucin (HSLM) from human sublingual gland, and have found that the deduced amino acid sequences can be aligned with the cysteine-rich carboxy-terminal region of human intestinal mucin MUC2, porcine submaxillary gland mucin, and bovine submaxillary gland mucin. The specific aims are to: 1. Characterize the structural organization of HSLM by determining the nucleotide and deduced amino acid sequences of the tandem repeat region, and the N-terminal and C-terminal regions flanking the repeats, the tissue distribution of transcripts, the chromosomal localization of the HSLM gene and the occurrence of HSLM homologues in other vertebrates. 2. Identify the high molecular weight mucin (HSMM) in submandibular gland by isolating clones for this mucin from a human submandibular gland cDNA library, determining the nucleotide and deduced amino acid sequences of the coding region, and examining the expression patterns, gene localization and evolutionary relationships of this mucin.